Dynode assembly for electron multiplier

ABSTRACT

A miniature electron multiplier having a pair of complementary dynode support elements formed of ceramic material, each of the elements having a plurality of longitudinally spaced-apart projections extending transversely outwardly from a side thereof and mutually defining outwardly facing recesses therebetween. The elements are disposed with their sides in spaced, parallel facing relationship with the projections of one element located generally midway between the projections of the other element and respectively extending toward the recesses of the other element but having their outer ends spaced from the side thereof so as to define a generally serpentine channel. A plurality of dynode elements formed of relatively thin sheet metal are respectively seated in the recesses and brazed to the walls thereof. Top and bottom plate elements formed of ceramic material secure the support elements in assembled relation and close the channel. The dynode elements have integral leads which extend outwardly between the respective support element and plate element to the exterior of the assembly where they may be attached to a voltage divider resistance printed upon the outer surface of one of the cover plates.

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ABSTRACT: A miniature electron multiplier having a pair of complementary, dynode support elements formed of ceramic material, each of the elements havin dinally spaced-apart projections ext wardly from a side thereof and mutuall facing recesses therebetween. The elem their sides in spaced, parallel facing rel jections of one element located generally midway between the projections of the other element and respectivel toward the recesses of the other element but havin outer ends spaced from the side thereof so as to define a generally serpentine channel. A plurality of dynode elements formed of relatively thin sheet metal are respectively seated in 5 4 4 MBMHmw nnwwn D n BO 3 M031 H u moo w m NH R m u C m m m W m E m m R m m 0 n F my U OJ. Y .1 u .UN L F m m n a g T B n n n A Wm M m m m m Mm a m m cN mm m L m m a Dmhm .n m w mmm o. M Y C S L M DM9 U h F M U H m .D U U r 1 [56] References Cited the recesses and brazed to the walls thereof. Top and bottom UNITED STATES PATENTS plate elements formed of ceramic material secure the support ements in assembled relation and close the channel. The 212575O 8/1938 dynode elements have integral leads which extend outwardl 313/105 38/103 X etween the respective support element and plate element t 313/105 X 3,229,143 1/1966 Bartschat.... 3,272,984 9/1966 Hertzogetal.

the exterior of the assembly where they may be attached to a voltage divider resistance printed upon the outer surface of one of the cover plates.

FOREIGN PATENTS 1,230,924 12/1966 Germany......................

PATENTEDNOV 9 18H 3,619.6 92

SHEET 1 OF 2 INVENTOR'. CYQIL L DAY,

ATTORNEYS.

PATENTEUNUV 91971 3.619.692

SHEEI 2 OF 2 INVENTOR: CYRIL. l. DAY

ATTORNEYS.

DYNODE ASSEMBLY FOR ELECTRON MULTIPLIER BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates generally to electron-multiplier devices, and more particularly to dynode assemblies therefor.

2. Description of the Prior Art Conventional electron multipliers comprise a plurality of discrete dynode stages connected to progressively increasing potentials. The dynodes are formed of or coated with secondary emissive material and arranged so the electrons injected into the low potential end of the device are multiplied by impact upon the initial dynode, thus resulting in acceleration of secondary electrons to the next successive dynode where the process repeats, thus giving rise to an overall, cascade multiplication of electrons. Conventional electron multipliers are enclosed in an evacuated envelope and the progressively increasing potentials are normally obtained from an external voltage divider resistance and applied to the dynodes through a stem or stems in the envelope. This construction, which involves independently and electrically isolated mounting of each of the dynodes, is complex and costly, and, further, the construction is fragile and not well suited to applications in which sudden jars and shocks may be encountered. In U.S. Pat. No. 3,244,922 to L. G. Wolfgang and assigned to the assignee of the present application, there is disclosed an electron-multiplier construction which eliminates the floating or free-standing dynodes of prior multipliers by employing a block of dielectric material having an undulated passage therein extending from end to end, opposite surfaces of the passage being coated with semiconductive secondary emissive material.

SUMMARY OF THE INVENTION It is desired to provide an electron-multiplier construction of small size which is extremely rugged and eliminates the free-standing dynodes of conventional multiplier construction and which is easily and economically assembled from readily produced component parts.

The invention, in its broader aspects, provides a dynode assembly including a pair of complementary dynode support elements formed of dielectric material and respectively having longitudinally spaced opposite ends, each of the support elements having a plurality of longitudinally spaced-apart projections extending transversely outwardly from a side thereof and mutually defining outwardly facing recesses therebetween. The support elements are disposed with their sides in spaced, parallel facing relationship and with the projections of one support element located generally midway between the projections of the other support element and respectively extending toward the recesses of the other support element but having their outer ends spaced from the side thereof, thereby defining a generally serpentine channel between the opposite ends of the support elements. A plurality of discrete metallic dynode elements are respectively seated in the recesses and engage the walls thereof, and means are provided for securing the support elements in assembled relation.

It is accordingly an object of the invention to provide an improved dynode assembly for an electron-multiplier device.

Another object of the invention is to provide an improved dynode assembly for an electron multiplier device which is rugged, which eliminates free-standing dynodes, and which is easily assembled.

BRIEF DESCRIPTION OF THE DRAWINGS The above mentioned and other features and objects of this invention and the manner of attaining them will become more apparent and the invention itself will be best understood by reference to the following description of an embodiment of the invention taken in conjunction with the accompanying drawings, wherein:

FIG. 1 is an exploded, perspective view illustrating one embodiment of the invention;

FIG. 2 is a cross-sectional view taken generally along the line 2-2 of FIG. 1 and further illustrating another feature of the invention;

FIG. 3 is a view in perspective illustrating the method of fabrication of the dynode elements employed in the embodiment of FIG. 1;

FIG. 4 is a top view, partly broken away, illustrating a further feature of the invention;

FIG. 5 is a cross-sectional view illustrating another embodiment of the invention;

FIG. 6 is an end view of the embodiment of FIG. 5 taken generally along the lines of 66 thereof;

FIG. 7 is a cross-sectional view taken generally along the lines of 7-7 of FIG. 5;

FIG. 8 is a perspective view showing the two dynode support elements of the embodiment of FIG. 5 in assembled relation; and

FIG. 9 is a perspective view showing one of the dynode elements of the embodiment of FIG. 5.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to FIGS. 1, 2, and 3 of the drawings, there is shown an embodiment of the invention, generally indicated at 10, comprising a pair of complementary dynode support elements 11 and 12, each formed of suitable ceramic material,

such as a high-alumina ceramic. Element 11 has spaced, parallel inner and outer sides 13 and I4, opposite ends, 15 and I6, and spaced, parallel top and bottom surfaces 17 and 18. Element 11 has an end projection 19 extending outwardly from its inner wall 13 at its end 15, and another, wider, end projection 20 extending transversely outwardly from its inner wall 13 at its other end 16. Longitudinally spaced, parallel, projections 22 and 23 extend transversely outwardly from inner side 13 of element 11, projections 19 and 22 mutually defining a generally rectangular recess 24, projections 22 and 23, mutually defining another generally rectangular recess 25, and projection 23 and 20 mutually defining yet another generally rectangular recess 26.

Element 12 has spaced, parallel inner and outer sides 27 and 28, opposite ends 29 and 30, and spaced, parallel top and bottom surfaces 32 and 33. An end projection 34 extends transversely outwardly from inner side 27 of element 12 and 30. Spaced, parallel projections 35 and 36 and 37 extend transversely outwardly from inner side 27 of element 12, projection 35 being spaced from end 29. Projections 35 and 36 mutually define a generally rectangular recess 38, projections 36 and 37 mutually define a generally rectangular recess 39, and projections 37 and 34 mutually define a smaller generally rectangular recess 40.

It will be seen that projections 22 and 23 of element 11 are respectively located generally midway between projections 35, 36, and 37 of element 12, projections 22 and 23 respectively extending into recesses 38 and 39, but having their outer ends transversely spaced from inner side 27 of element 12, and projections 35, 36, and 37 respectively extending into recesses 24, 25, and 26, but having their outer ends likewise transversely spaced from inner side 13 of element 11. It will thus be seen that projections 19, 22, and 23 of element 11, on the one hand, and projections 35, 36, and 37 of element 12, on the other hand, mutually define a generally serpentine channel 42 having an open end 43 defined by end projection 19 of element 11 and end 29 of element 12, and a closed end 44 defined by end projections 20 and 34.

Each of the recesses, 24, 25, 26, 38, 39, has a pair of dynode elements 45 and 46 seated therein abutting the respective projection and side 13, 27. Dynodes 45, 46 are formed of relatively thin sheet metal having secondary emission properties, such as 0.002 to 0.003 inch beryllium copper. The interior walls of the recesses 24, 25, and 26, 38, and 39 are preferably first metallized, and the dynode elements 45 and 46 are then brazed thereto, thus securely attaching the dynode elements to the walls of the respective recesses. An initial dynode element 47 and a final dynode element 48 are similarly formed and attached to projections 35 and 37, respectively, and to inner side 27 of element 12 as shown in FIG. 2. An output electrode 49 is similarly attached to the inner surface of end projection 34 of support element 12, as shown. Each of the dynode elements 45, 46, 47, and 48 has an external lead 50 integrally formed thereon.

Referring briefly to FIG. 3, the dynode element 45, 46 may be preformed from foil ribbon and jigged to the desired configuration as a single element 52, which is then cut along the dashed line 53 to form two separate dynode elements 45 and 46. Alternately, the dynode elements may be formed separately. It will be readily understood that other metals having secondary emission properties, or coated with secondary emission materials, may be employed for the dynode elements.

As shown in FIG. 1, external lead 50 of each of the dynode elements has a portion 54 which is folded over to extend outwardly over the upper surface 17, 32 of the respective support element 11, 12 and in engagement therewith. Top and bottom cover plates 55 and 56, are provided, also preferably formed of suitable ceramic material, and have a configuration conforming to that of the assembled support elements 11 and 12. The top cover plate 55 is positioned abutting the upper surface I7, 32 of the support elements 11, 12, with the outwardly extending portions 54 of the dynode element leads 50 being sandwiched therebetween. The bottom cover plate 56 is similarly positioned abutting the bottom surfaces 18, 33 of the support elements ll, 12. The dynode support elements 11, 12 and the top and bottom cover plates 55 and 56 are held in an assembled relation by a pair of through-bolts 57 extending through apertures 58 in the top cover element 55, apertures 59 in the end projections and 34, and corresponding apertures (not shown) in the bottom cover plate 56, suitable nuts 60 being secured to the bolts 57 so as to secure the top and bottom plates 55, 56, and the dynode support elements ll, 12 in assembled relation.

Portions 54 of the dynode element leads 50 may merely extend outwardly beyond the outer sides 14 and 28 of the dynode support elements 1 l and 12, thus forming terminals to which electrical connections to a separate voltage dividing resistor may be made. ln the illustrated and preferred embodiment, a suitable voltage dividing resistor 62 is printed in conventional fashion upon the upper surface 63 of the top cover plate 55. Portions 64 of the dynode element leads 50 which extend outwardly from portions 54 are then folded over the edges 65 of the top cover plate 55 and attached at appropriate points on the printed resistor 62, as by spot welding, thereby to apply appropriate potentials to the dynode elements when resistor 62 is coupled across a suitable source of potential.

It will be readily understood that appropriate resistors may be printed on both of the top and bottom cover plates 55 and 56 with certain of the external leads 50 of the dynode elements 45, 46 extending outwardly between the bottom surfaces 18, 33 of the dynode support elements ll, 12, and the bottom cover plate 56, for attachment to the resistor printed on the bottom cover plate. Alternatively, resistance elements may be printed on either or both of the outer sides 14, 28 of the dynode support elements ll, 12 with the external leads 50 of the dynode element attached thereto as desired,

As best seen in FIG. 2, slots 65, 66 are preferably formed in the inner sides 13, 27 of the dynode support elements 11, 12 between the adjacent edges of the respective dynode elements 45, 46, slots 65, 66 inhibiting the electrons from charging the insulating space between the adjacent edges of the dynode elements.

As an alternative to integrally forming external leads 50 on the dynode elements 45, 56, as above-described, suitable wire leads may be spot welded to the outer surfaces of the dynode elements as suggested by dashed line 67 in FIG. 2, and brought out through suitable holes drilled in the dynode support elements ll, 12, as suggested by the dashed lines 68. It will be readily understood that the recesses and the dynode elements seated therein may have other configurations, such as semicircular.

Referring now to FIG. 4, suitable potential wires 69 may be positioned at appropriate locations in the channel 42 for shaping the field, the wires 69 being brought out through suitable holes 70 drilled in the top cover plate 55, the extension portion 72 of the wire 69 being attached, as by spot welding, to appropriate dynode leads 64, as by spot welding. It will be understood that with the addition of the field-shaping wires 69, a box and grid-type multiplier construction is provided.

Referring now to FIGS. 59, another embodiment of the invention is shown, generally indicated at 73, comprising a pair of complementary dynode support elements 74 and 75 formed of suitable ceramic material. Each of the dynode support elements 74, 75 has a plurality of spaced-apart, semicircular recesses 76 formed therein respectively defining projections 77 therebetween. Anode support elements 74, 75 are again disposed in facing relationship with the projections 77 of one element located generally between the projections of the other element and respectively extending toward the recesses 76 of the other element, but having their outer ends spaced from the bottom of the recess, as seen in FIG. 5. In this embodiment, semicircular dynode elements 78 again formed of suitable relatively thin sheet metal are provided respectively seated in the recesses 76 and attached thereto, as by brazing as above described. It will be observed that the ends 79, 80 of each dynode element 78 extend forwardly from the respective projection 77 in order to minimize charging of the projections.

The dynode support elements 74, 75 are semicircular in cross section and when in assembled relation, define a cylinder. Dynode elements 74, 75 are received within an outer tube 82 formed of suitable ceramic material and having a longitudinally extending slot 83 formed therein communicating with the channel 81 defined by the recesses 76 and projections 77 of the dynode support elements 74, 75. Each of the dynode elements 78 has an integral external lead 84 which is brought out through the slot 83, as shown. As in the case of the embodiment of FIG. 1, a suitable voltage dividing resistance may be conventionally printed upon the outer surface of the ceramic tube 82 with the external lead 84 being attached at appropriate points thereon, as by spot welding.

When assembled within the ceramic tube 82, the opposite ends 85, 86 of the dynode support elements 74, 75 are generally flush with the opposite ends 87, 88 of the tube. Semicircular metal mounting plates 89, 90 are attached, as by brazing, to the opposite ends 85, 86 of the dynode support elements 74, 75, and complementary, part annular, metal mounting plates 92 are similarly attached, as by brazing, to the opposite ends 87, 88 of ceramic tube 82. It will be observed that the mounting plates 89, 90 attached to the opposite ends of the dynode support elements 74, 75 fit snugly within the annular metal mounting plates 92 at the opposite ends of the ceramic tube 82, being welded thereto, as seen at 93, 94 in FIG. 6, thereby retaining the dynode support elements 74, 75 and the tube 82 in assembled relation.

in the illustrated embodiment, a transparent faceplate 95 is secured at the initial or entrance end 96 of the dynode assembly 73 and has a suitable photocathode 97 formed on its inner surface in the channel 81. An output electrode eiement 98 may be secured at the other end of the device closing the channel 81 as shown.

It will be readily seen that the muitiplier assemblies of both embodiments are particularly suited for use as nude multipliers," i.e., use in environments where no air is present. However, it will be understood that the multiplier assembly of either embodiment may be mounted within an evacuated envelope for use in conventional environments. It will also be readily seen that the multiplier construction of the invention completely eliminates conventional floating or free-standing dynodes and the accompanying leads and stems, thus providing an extremely rugged construction. It will further be seen that the device is simply assembled from a small number of readily fabricated component parts.

While there have been described above the principles of this invention in connection with specific apparatus, it is to be clearly understood that this description is made only by way of example and not as a limitation to the scope of the invention.

What is claimed is:

1. In an electron-multiplier device, a dynode assembly comprising: a pair of complementary dynode support elements fonned of dielectric material and respectively having longitudinally spaced opposite ends, each of said support elements having a plurality of longitudinally spaced-apart projections extending transversely outwardly from a side thereof and mutually defining outwardly facing recesses therebetween, said support elements being disposed with said sides in space, parallel, facing relationship and with the projections of one support element located generally midway between the projections of the other support element and respectively extending toward the recesses of the other support element but having their outer ends spaced from the side thereof thereby defining a generally serpentine channel between said opposite ends; a plurality of discrete metallic dynode elements respectively seated in said recesses and engaging the walls thereof, the adjacent ends of the dynodes in said recesses on each said support element being spaced apart longitudinally; and means for securing said support elements in assembled relation.

2. The assembly of claim 1 wherein said dynode elements are of relatively thin sheet metal, the walls of said recesses having a metallized coating thereon and said dynode elements being brazed thereto.

3. The assembly of claim 1 wherein each of said support elements has spaced, parallel top and bottom surfaces normal to the respective side, said top and bottom surfaces being respectively coplanar when said support elements are in assembled relation, said securing means comprising top and bottom plate elements fonned of dielectric material and respectively abutting said top and bottom surfaces and closing said channel, and fastener means for respectively securing said plate elements to said support elements.

4. The assembly of claim 1 further comprising a field-shaping electrode located in each of said recesses and having a lead extending through and supported by said securing means.

5. The assembly of claim 1 wherein there are two of said dynode elements in each of said recesses respectively extending from adjacent the outer end of a respective projection to adjacent the midpoint of the respective recess, said two dynodes having closely spaced adjacent edges.

6. The assembly of claim 5 wherein each of said support elements has a slot formed in its said side in a respective recess between the adjacent edges the respective two dynode elements.

7. The assembly of claim 1 wherein said support elements are formed of ceramic material, said dynode elements being formed of relatively thin sheet metal and being attached to the walls of said recesses; each of said support elements having spaced, parallel top and bottom surfaces normal to the respective side, said top and bottom surfaces being respectively coplanar when said support elements are in assembled relation, said securing means comprising top and bottom plate elements formed of ceramic material and respectively abutting said top and bottom surfaces and closing said channel, and means for respectively securing said plate elements to said support elements; each of said dynode elements having an integral lead extending therefrom outwardly between a respective surface and plate element to the exterior of said assembly.

8. The assembly of claim 1 wherein each of said recesses has a generally rectangular configuration.

9. The assembly of claim 1 including a transparent faceplate and photocathode enclosing one end of said channel and an output electrode at the other end. 

1. In an electron-multiplier device, a dynode assembly comprising: a pair of complementary dynode support elements formed of dielectric material and respectively having longitudinally spaced opposite ends, each of said support elements having a plurality of longitudinally spaced-apart projections extending transversely outwardly from a side thereof and mutually defining outwardly facing recesses therebetween, said support elements being disposed with said sides in space, parallel, facing relationship and with the projections of one support element located generally midway between the projections of the other support element and respectively extending toward the recesses of the other support element but having their outer ends spaced from the side thereof thereby defining a generally serpentine channel between said opposite ends; a plurality of discrete metallic dynode elements respectively seated in said recesses and engaging the walls thereof, the adjacent ends of the dynodes in said recesses on each said support element being spaced apart longitudinally; and means for securing said support elements in assembled relation.
 2. The assembly of claim 1 wherein said dynode elements are of relatively thin sheet metal, the walls of said recesses having a metallized coating thereon and said dynode elements being brazed thereto.
 3. The assembly of claim 1 wherein each of said support elements has spaced, parallel top and bottom surfaces normal to the respective side, said top and bottom surfaCes being respectively coplanar when said support elements are in assembled relation, said securing means comprising top and bottom plate elements formed of dielectric material and respectively abutting said top and bottom surfaces and closing said channel, and fastener means for respectively securing said plate elements to said support elements.
 4. The assembly of claim 1 further comprising a field-shaping electrode located in each of said recesses and having a lead extending through and supported by said securing means.
 5. The assembly of claim 1 wherein there are two of said dynode elements in each of said recesses respectively extending from adjacent the outer end of a respective projection to adjacent the midpoint of the respective recess, said two dynodes having closely spaced adjacent edges.
 6. The assembly of claim 5 wherein each of said support elements has a slot formed in its said side in a respective recess between the adjacent edges the respective two dynode elements.
 7. The assembly of claim 1 wherein said support elements are formed of ceramic material, said dynode elements being formed of relatively thin sheet metal and being attached to the walls of said recesses; each of said support elements having spaced, parallel top and bottom surfaces normal to the respective side, said top and bottom surfaces being respectively coplanar when said support elements are in assembled relation, said securing means comprising top and bottom plate elements formed of ceramic material and respectively abutting said top and bottom surfaces and closing said channel, and means for respectively securing said plate elements to said support elements; each of said dynode elements having an integral lead extending therefrom outwardly between a respective surface and plate element to the exterior of said assembly.
 8. The assembly of claim 1 wherein each of said recesses has a generally rectangular configuration.
 9. The assembly of claim 1 including a transparent faceplate and photocathode enclosing one end of said channel and an output electrode at the other end. 